Lord Embros, 2nd Epic Boss encounter, is immune to magic and melee attack. Definitely to melee, resists all magic thrown at him. Wasted a good hour plugging away with various attacks. Poisons and procs hit but have zero impact on the health bar. I pulled him over every conceivable piece of real estate to test if there was a spot where he can be attacked without immunity. There is none.

Also should weigh the impact of camping the entrance port in permanently verses immunity increased timer. I farmed a guy there non stop tonight.